Heatable roller

ABSTRACT

A heatable roller which can be heated from inside the roller body by a heating device. Provided radially outside the heating device are axially parallel bore holes uniformly distributed over the periphery of the roller body which are connected at the ends by annular chambers. The bore holes and the annular chambers form a closed system which is partially filled with water. This system operates to make the temperature uniform via condensation heating in the event of local temperature reduction.

FIELD OF THE INVENTION

The invention relates to a heatable roller of the type having acylindrical roller body rotatably mounted about its axis, the rollerbody having a first cavity disposed therein, and a second cavitydisposed radially outside of the first cavity. The first cavity has aheating device extending over a length of the heatable roller. Thesecond cavity includes a plurality of elongated channels uniformlydistributed over the periphery of the roller body partially filled witha liquid that vaporizes at a temperature produced by the heating device.

BACKGROUND OF THE INVENTION

Such a roller is known from a company publication of the Japanese firmTokuden. Provision is made inside the roller, coaxially to its axis, fora coil arrangement which heats the roller body inductively from inside.Disposed radially outside of the coil arrangement in the roller body arebore holes which are parallel to the axis and are partially filled withwater, because water has the greatest evaporation heat and, thus, thegreatest temperature-adjustment effect during condensation. The boreholes are each closed individually at the ends in a pressure-resistantmanner. If a temperature drop occurs at a bore-hole location duringoperation, the vapor in the free space of the hollow chamber not filledby water condenses there and produces a condensation temperature-risewhich immediately brings the location in question to the temperature ofthe ambient environment. Thus, there is an automatic equalization oftemperature over the roller-body surface.

The elongated channels can be produced in the roller body at relativelylow cost using known means, leaving the stability of the roller bodyessentially intact. The expression "elongated channel" is used to implythat the cross-section is not important, and that the channels have alength amounting to a multiple, e.g. 20 to 150 times, thecross-sectional dimension. In practice, they are "peripheral" bore holesintroduced into the roller body near the outer periphery.

Axially parallel bore holes have been known for quite some time inconnection with the heating of rollers. For example, German UtilityModel Patent 90 14 117 discloses axially parallel bore holes, that,however, do not form a closed system, but rather are traversed by theflow of a heat-carrier liquid which is heated outside of the roller andtransferred by pumping. In the German 40 33 986 A1, bar-shaped,electrical heating elements are arranged in the peripheral bore holes.

In the specific embodiment of the species, the elongated channels mustbe individually partially filled to a specific level with water and thensealed off in a pressure-tight manner. In addition, after beingpartially filled with water, the channels must be evacuated, sinceotherwise air pockets form in the channels and hinder vaporcondensation. Because evacuation is necessary, only individually sealingoff the channels by welding them closed or by using screw plugs comesinto consideration. This requires a considerable expense which may haveto be repeated over the service life of the roller. For example, whenthe roller must be re-engraved, the surface must be heat-treated, makingit necessary to empty the elongated channels. It is then necessary torefill the elongated channels with precisely measured volumes of water,and subsequently to evacuate them. The volume of water in each elongatedchannel should conform, otherwise the condensation heating of theindividual channels will not create uniform heating over the peripheryof the roller body.

SUMMARY AND OBJECTS OF THE INVENTION

The underlying object of the invention is the further development of aroller of this general type that will improve its properties duringoperation and reduce expenditure when starting up or shutting downoperation.

This objective is fulfilled by providing a heatable roller of the typehaving a cylindrical roller body rotatably mounted about its axis, theroller body having an outer periphery that forms a working rollerperiphery, a first cavity arrangement disposed therein, and a secondcavity arrangement disposed radially outside of the first cavityarrangement. The first cavity arrangement has a heating device extendingover a length of the heatable roller in its longitudinal direction, atleast over a working width of the heatable roller. The second cavityarrangement has a plurality of elongated channels, the plurality ofelongated channels being axially parallel, more holes closed at theends, uniformly distributed over the periphery of the roller body, andpartially filled with a liquid that vaporizes at a temperature producedby the heating device. The heatable roller further provides an annularchamber that interconnects the plurality of elongated channels on an endof the plurality of elongated channels, the annular chamber having aseparate, sealable inlet channel accessible from outside the heatableroller.

The elongated channels distributed over the periphery are interconnectedby an annular chamber. This arrangement ensures that the water volumesin the individual channels are automatically adjusted during operation,thus providing for an even temperature distribution over the peripheryof the roller. The annular chamber also simultaneously offers thecapability of filling and emptying all the axially parallel channels atone time using a single inlet channel, as well as the capability ofproducing a vacuum in all the channels. Thus, it is no longer necessaryto fill the channels individually, while taking care that the watervolumes are identical; rather, it is only necessary to supply or removea single quantity of water at one location. Another important advantageis that all of the axially parallel channels are sealed off at thissingle location, that is, the inlet channel, to form a closed system.

Taken by themselves, annular chambers into which axially parallelchannels open are known from the German patents 33 26 746 A1 and 38 38726 A1. However, the known specific embodiments do not have a closedchannel system, but rather, the axially parallel channels are traversedby the flow of a heat-carrier liquid.

The channels may be expediently designed such that the annular chamberradially overlaps a cross-section of the plurality of elongatedchannels.

One refinement of the invention which is important in practice dealswith producing the annular groove in a manner that can be justified interms of manufacturing.

This can be carried out advantageously by having the annular chamberformed by an annular recess introduced at an end of the roller body, theannular recess being in fluid communication with the ends of theplurality of elongated channels. The annular groove can be produced bymeans of a ring-shaped recess that is closed by a retaining ring.Alternatively, the annular groove can also be produced by an innerperipheral offset at the end of the roller body, the inner peripheraloffset being closed axially to the outside and radially to the inside byan angular retaining ring.

Since the retaining rings and the plugs are impervious to the fluid theyare to contain and, in some instances, must be able to withstand highpressures, it is advisable to weld them along their jointing zone, i.e.along the two longitudinal edges of the retaining rings and at theperiphery of the plugs.

In the preferred exemplary embodiment of the invention, the cylindricalroller body has attached roller journals. In accordance with oneembodiment of the invention, roller journals can be so configured thatthey cover the jointing zone, so that even in the event of a burstwelding seam, the damage location is contained by the roller journal,thus preventing parts from scattering explosively under high vaporpressure.

The roller journal can be designed, for example, such that it includesan end surface which is transverse to the axis of the roller body, theend surface making contact against an end face of the roller body, and acylindrical centering collar engaging with the end of the roller body,and wherein the roller journal covers the jointing zones of the weldsfor the plugs and retaining rings of the heatable roller.

The roll journals may be axially-equal or coaxial with the roller body,and the inlet channel can run through a wall of the roller journal anddischarge in the end area of the roll journal. The inlet channel mayalso discharge in an end face of the roll journal or axle journal, theend face being overlapped by the cover plate such that the inlet channelis sealable in a rotatably fixed manner.

According to a further embodiment of the invention, the end plate canhave a sealable connection which is in communication with the inletchannel in the roller journal via a connecting channel formed in the endplate.

Another advantage of the annular-chamber arrangement is that all theaxially parallel channels can be safeguarded simultaneously by onesingle pressure-relief safety mechanism which can be constructed andmounted such that a pressure-relief safety mechanism having a rupturedisk is inserted in the sealable connection, located, for example, inthe cover plate, and wherein the pressure-relief safety mechanism sealsthe sealable connection.

The arrangement of a vacuum check valve, for example, in a connectingchannel on the inner side of a pressure relief valve of the roller isuseful in order to be able to retain the vacuum following evacuation ofthe channels that are partially filled with water. In this manner,evacuation can be carried out at the connection and the vacuum ismaintained when the vacuum pump is removed from the connection. Thevacuum is maintained while the pressure relief valve is inserted intothe connection, generally by screwing it in. When the pressure in theaxially parallel channels rises in response to an increase intemperature, the vacuum check valve opens and the pressure is relievedby the pressure relief valve.

In principle, the first cavity arrangement which accommodates theheating device can likewise be an arrangement of axially parallel boreholes in the roller body and provided radially inside the second cavityarrangement. However, in the preferred specific embodiment of theinvention, the first cavity arrangement comprises a single cavitydisposed coaxially to the axis.

In a first alternative embodiment, the heating device can comprise aheat-carrier medium that flows lengthwise through the roller body viathe more proximate, individual, axially parallel bore holes mentionedabove, or in the single available cavity (either via a special heatingbody, or via an arrangement in which the heat-carrier medium completelyfills up the central cavity).

Alternatively, the heating device can also comprise an electricalheating apparatus, for example, in the form of electrical resistanceheating-rods or an induction heating apparatus.

If the heating apparatuses are arranged in the single central cavitythat is coaxial to the axis of the roller body, they can rotate with theroller body and can be provided with energy by way of at least one swingjoint as is described, taken by itself, for resistance-heated radiantheating elements from the essay by Wagner "Die elektrischeWalzenheizung" [Electrical Roller Heating] in "die elektrischeAusrustung" [Electrical Equipment] (Vogel Publishing House, Wurzburg)No. 2 of Apr. 20, 1966.

However, according to a further embodiment of the present invention, itis also possible to mount the heating device non-rotatably, which savesthe swing joint, and to support the heating device pivotally in thecoaxial, central cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal, cross-sectional view taken along the axis ofan embodiment of a heated roller constructed according to the principlesof the invention.

FIG. 2 is a partial cross-section taken along line II--II in FIG. 1;

FIG. 3 is a partial longitudinal section through an end area of aroller;

FIG. 4 is a view taken along the line IV--IV in FIG. 3; and

FIGS. 5 and 6 provide views similar to those of FIGS. 3 and 4, foranother embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The roller, denoted as a whole by reference numeral 100, comprises acylindrical, steel roller body 10 with a working roller-periphery 1 andan axis 2, the roller body 10 having outwardly protruding rollerjournals 3 at both ends, recessed to a smaller diameter, upon which arearranged bearings 4 for supporting roller 100 in a machine frame or thelike. As first cavity arrangement H₁, roller body 10 contains a single,cylindrical, inner cavity 5 which is coaxial to axis 2 and in which isarranged an electrical heating device 20. In the exemplary embodimentshown, the heating device 20 is fixed relative to roller body 10 andturns with the roller body 10. The heating device 20 comprises aplurality, e.g. six or eight, axially parallel, electrical resistanceheating rods or heating elements 21 on a divided circle, uniformlydistributed over the periphery of the inner cavity 5. The heating rods21 are braced in their mutual arrangement by means of holding disks 22arranged with axial clearances. The heating rods 21, as shown at theleft end of the drawing, extend through an end plate 6 of roller 100. Aslip-ring arrangement 14 is provided outside of the roller 100 by whichcurrent may be introduced to heat the heating elements 21. Analternative heating device 20 (which corresponds to a possible specificembodiment not shown) may be arranged non-rotatably inside the rollerbody, such that roller body 10 rotates relative to the heating device20. In that case, the slip-ring arrangement 14 is not needed and fixedconnections can be used to supply the heating energy. Heating device 20forms an enclosed unit which, after releasing end plate 6, can be pulledto the left out of roller 100, e.g. in case individual heating rods 21are defective and need to be replaced.

Heating device 20 heats by radiating the peripheral area of cavity 5.The heat is transported radially to the outside by conductance and, atouter periphery 1 of roller 100, is transferred onto the fabric web tobe processed. The goal is to have as uniform a temperature distributionas possible at outer periphery 1, primarily in the longitudinaldirection of roller 100, but also in the circumferential direction.

The uniformity of the temperature distribution can be disturbed eitherif the heating rods 21 work unevenly, or if the fabric web picks upuneven amounts of heat, for instance, due to uneven moisture contents.

To counteract the unevenness of the temperature distribution, a secondcavity arrangement H₂ is provided in roller body 10 radially outside ofcavity 5. Cavity arrangement H₂ is in the form of axially parallel boreholes 30 which are uniformly distributed over the periphery. The boreholes 30 are arranged on a divided or broken circle and have equaldiameters. In the exemplary embodiment, the bore holes 30 are locatedbelow the outer periphery 1 by a distance approximately equal to thelength of their diameter, and they retain a corresponding unobstructedclearance from one another in the circumferential direction.

Near the ends of the cylindrical roller periphery 1, bore holes 30 areinterconnected by annular chambers 31 which extend in a plane transverseto axis 2. In the exemplary embodiment, the annular chambers 31 have arectangular cross-section in a sectional plane through axis 2. The flankadjacent to bore holes 30 extends radially somewhat beyond theboundaries of the bore holes 30 both inwardly and outwardly, so thattheir cross-section is overlapped by annular chambers 31.

The right annular chamber 31 in FIG. 1 has an inlet channel 16 whichextends through axle journal 3 and discharges at end face 15 of axlejournal 3 at 16'.

End face 15 is covered by a cover plate 7 in which is formed aconnecting channel 19. At its first end, connecting channel 19discharges at location 19' opposite location 16' and, in this manner,communicates with inlet channel 16. At its other end, connecting channel19 opens into a connection 18 which, in the exemplary embodiment, isformed as a tap hole 18 coaxial to the axis 2. Screwed into the tap hole18 in the state shown in FIG. 1 is a pressure-relief safety mechanism33, with a rupture disk, which seals the entire system of channels 30and annular chambers 31 to the outside.

Provided on the inside of pressure-relief safety mechanism 33 or ofconnection 18 is a vacuum check valve 23, indicated only schematicallyin FIG. 1, which opens outwardly.

Connection 18 is also used for filling the system with water 8, foremptying the system of water 8, and for evacuating the system after thewater has been admitted. After the evacuation, the vacuum connection isunscrewed from connection 18, whereupon vacuum check valve 23 maintainsthe vacuum. Pressure-relief safety mechanism 33 can then be screwed in.

Bore holes 30 and annular chambers 31 form a closed system that ispartially filled with water, in which the pressure rises in conformancewith the temperature therein.

During operation, thus when roller 100 is rotating at a considerablespeed, water 8, under the action of centrifugal force, is forced againstthe outer boundary of bore holes 30 and forms a cylindrical, inner level9. As soon as a lower temperature occurs at one location of thewater-free inner boundary of bore hole 30, water vapor condenses thereand raises the temperature of that location. Thus, water 8 in thepartially filled bore holes 30 functions as an automatic temperaturecompensation.

The temperature of water 8 can be detected by a thermal sensing device11 which, when the roller is in motion, is situated outside of innerlevel 9 of water 8 and thus within the water 8. The signal of thethermal sensing device 11 is routed via a plug connection 12 to one ofthe slip rings of slip-ring arrangement 14.

Two modifications are indicated with dotted lines in the drawing ofFIG. 1. Shown in the upper half as a possible alternative first cavityarrangement H₁ are axially parallel bore holes 13 which are locatedradially inward from the bore holes 30 and which are distributed overthe periphery, through which, optionally, in a manner known in the art,a heat-carrier medium may be routed in a meander-shaped liquid guidanceThis type of heating can replace heating device 20. The othermodification comprises a cylindrical enlargement 5' of cavity 5 in theworking area of roller periphery 1 and coaxial to axis 2. Cavity 5reduces the wall thickness of roller body 10 in this area, thusshortening the radial distance through which the heat applied to theinner circumference of roller body 10 has to be transported byconductance.

FIGS. 3 to 6 show possible practical implementations of annular chambers31 at the ends of longitudinal bore holes 30. In these embodiments,roller journals 3 are added on as separate parts to the actualcylindrical roller body 10.

As is illustrated in FIG. 3, longitudinal bore holes 30 forming thechannels in cylindrical roller body 10 are introduced from the end face1' of roller body 10 that is transverse to axis 2.

An inner circumferential groove 24, which in the exemplary embodimenthas a substantially U-shaped cross-section, is introduced from the innercircumference 1" of the end of roller body 10 into the end and cuts intolongitudinal bore holes 30. A wall thickness of 10 to 30 mm remainsbetween the outer right flank 24' of circumferential groove 24 in FIG. 3and end face 1' of roller body 10. Longitudinal bore holes 30 continuethrough this wall thickness, which remains from their production, andare all imperviously sealed by welded-in plugs 25. The jointing zone,i.e., the annular weld, is indicated in the figure via reference numeral26.

The inside width of circumferential groove 24 is radially overlappedinwardly by a retaining ring 27 having an approximately rectangularcross-section, the longer rectangle sides extending parallel to axis 2.At the two short rectangle sides, retaining ring 27 is welded by welds28 and 29 to the end of roller body 10 or to the inner edge of wallsection 33.

With an end surface 3' that is transverse to the axis, the separateroller journal 3 is placed against end face 1' of roller body 10 and issecured there by axially parallel screws 34 (see FIG. 4), which aredistributed over the periphery. Roller journal 3 has an axiallyprojecting centering-collar 35 which, with its outer peripheral surface,lies from inside against an inner peripheral section 36 of roller body10, and especially against the inner circumference of retaining ring 27.

Thus, roller journal 3 covers the jointing zones, configured as welds26, 28, 29, from the outside, opposite those in longitudinal bore holes30 and in the circumferential groove 24 which has become annular groove31 because of retaining ring 27, so that, in the event that one of thewelds fails, no parts can be hurled outwardly.

In the specific embodiment shown in FIGS. 5 and 6, an inner shoulder,having a cylindrical, outside wall section 37 and a shoulder-like wallsection 38 projecting inwardly and transversely to axis 2 thus formingan inner peripheral offset, is screwed into end face 1' of roller body10. Longitudinal bore holes 30 are introduced into the shoulder-likewall section 38, which thus extends over the entire cross-section of thelongitudinal bore holes 30. After completion of the longitudinal boreholes, an angular retaining ring 40 is welded in a cross-section thattraverses the axis. One radial leg 41 of the retaining ring forms theflank of annular groove 31 opposite shoulder 38, while the other leg 42represents the radially inner delimitation of annular groove 31.Retaining ring 40 is welded at both of its edges by welds 43, 44 to theouter edge of cylinder surface 37 or to the inner edge of shouldersurface 38.

The jointing zone formed by welds 43, 44 is covered, in the same manneras in the exemplary embodiment of FIGS. 3 and 4, by end surface 3' thatis transverse to axis 2, and outer periphery 35' of centering collar 35.39 is a pressure-relief bore hole which starts from the apex between endsurface 3' and outer periphery 35' of centering collar 35 as shown inthe drawing.

What is claimed is:
 1. A heatable roller, comprising:a cylindricalroller body, rotatably mounted about its axis, having an outer peripherythat forms a working roller periphery, a first cavity arrangementdisposed therein, and a second cavity arrangement disposed radiallyoutside of the first cavity arrangement; the first cavity arrangementhaving a heating device extending over a length of the heatable rollerin its longitudinal direction, at least over a working width of theheatable roller; the second cavity arrangement having a plurality ofelongated channels, the plurality of elongated channels being axiallyparallel, closed at the ends, uniformly distributed within the rollerbody near the outer periphery of the roller body, and partially filledwith a liquid that vaporizes at a temperature produced by the heatingdevice; and an annular chamber that interconnects the plurality ofelongated channels on an end of the plurality of elongated channels, theannular chamber having a separate, sealable inlet channel accessiblefrom outside the heatable roller.
 2. The roller as defined by claim 1,wherein the annular chamber radially overlaps a cross-section of theplurality of elongated channels.
 3. The roller as defined by claim 1,wherein the annular chamber is formed by an annular recess introduced atan end of the roller body, the annular recess being in fluidcommunication with the ends of the plurality of elongated channels. 4.The roller as defined by claim 3, wherein the annular chamber comprisesan inner circumferential groove starting from an inner circumference ofan end of the roller body and cutting into the ends of the plurality ofelongated channels, the inner circumferential channel being closed by aretaining ring covering an inside cross-section of the innercircumferential groove radially to the inside, the plurality ofelongated channels passing through an outer flank of the innercircumferential groove, and the plurality of elongated channels beingaxially closed by plugs inserted in the ends thereof.
 5. The roller asdefined by claim 4, wherein the retaining ring and plugs are weldedalong joining zones.
 6. The roller as defined claim 5, furthercomprising a roller journal attached to an end of the roller body, theroller journal covering the jointing zones.
 7. The roller as defined byclaim 6 wherein the roller journal comprises:an end surface which istransverse to the axis of the roller body, the end surface makingcontact against an end face of the roller body; and a cylindricalcentering collar engaging with the end of the roller body.
 8. The rolleras defined by claim 3, wherein the annular chamber comprises an innerperipheral offset at the end of the roller body, the inner peripheraloffset being closed axially to the outside and radially to the inside byan angular retaining ring.
 9. The roller as defined by claim 1, whereinthe roller body has coaxial roller journals at the ends thereof, and theinlet channel extends through a wall of one of the roller journals anddischarges in an end area of the roller journal.
 10. The roller asdefined by claim 9, wherein the inlet channel discharges out an end faceof one of the roller journals, and the end face is overlapped by a coverplate, the cover plate sealing the inlet channel in a rotatably fixedmanner.
 11. The roller as defined by claim 10, wherein a sealableconnection is formed in the cover plate, the sealable connectioncommunicating with the inlet channel via a connecting channel formed inthe cover plate.
 12. The roller as defined by claim 11, furthercomprising a pressure-relief safety mechanism having a rupture disk, thepressure-relief safety mechanism being inserted in and sealing thesealable connection.
 13. The roller as defined by claim 12, furthercomprising a vacuum check valve disposed in the connecting channelbetween the pressure-relief safety mechanism and the annular chamber.14. The roller as defined by claim 1, comprising means to protect theannular chamber against excessively high pressures.
 15. The roller asdefined by claim 14, further comprising a pressure-relief safetymechanism having a rupture disk, the pressure-relief safety mechanismbeing inserted in and sealing the sealable connection.
 16. The roller asdefined by claim 1, wherein the first cavity arrangement comprises asingle cavity coaxial to the axis of the roller body.
 17. The roller asdefined by claim 16 wherein the heating device is arranged non-rotatablyand is pivotally supported in the single cavity.
 18. The roller asdefined by claim 1, wherein the heating device comprises a heat-carriermedium flowing lengthwise through roller body.
 19. The roller as definedby claim 1, wherein the heating device comprises an electrical heatingapparatus.
 20. The roller as defined by claim 1, wherein the heatingdevice comprises electrical resistance heating rods.
 21. The roller asdefined by claim 1, wherein the heating device is an induction device.22. The roller as defined by claim 1, wherein the heating device rotateswith roller body and is energized by way of at least one swing joint.23. A heatable roller assembly, comprising:a cylindrical roller body,rotatably mounted about a longitudinal axis, said roller body having anouter peripheral surface, a first cavity disposed therein, and a secondcavity arrangement disposed radially outside of the first cavityarrangement, the second cavity arrangement havinga plurality ofelongated channels, the plurality of elongated channels being axiallyparallel, closed at the ends, uniformly distributed along a region nearthe outer peripheral surface of the roller body, and partially filledwith a liquid that vaporizes at a temperature produced by the heatingdevice; and an annular chamber that interconnects the plurality ofelongated channels on an end of the plurality of elongated channels, theannular chamber having a separate, sealable inlet channel accessiblefrom outside the heatable roller; a seal for selectively closing theinlet channel; a heating device located within the first cavity thatextends over a length of the roller body for at least a working width ofthe roller body; and a roller journal at each end of the roller body.